During the past decade, many nucleoside analogs have been found to exhibit good antitumor and antiviral activities. Among the presently known synthetic nucleosidic antiviral agents, the more important generally are considered to be 5-iodo-2'-deoxyuridine (IDU), 9-.beta.-D-arabinofuranosyladenine (ara-A), and 1-.beta.-D-arabinofuranosylcytosine (ara-C). These compounds, however, are only active against a limited spectrum of viruses which does not include those causing respiratory diseases in man (influenza, common cold). The only nucleosidic analog of which we are aware that is active against these respiratory disease viruses is 1-.beta. -D-ribofuranosyl-1,2,4-triazole-3-carboxamide which is described in our copending United States patent application, Ser. No. 240,252, filed Mar. 31, 1972, entitled 1,2,4-Triazole Nucleosides, which application is a continuation in part of Ser. No. 149,017, filed June 1, 1971, entitled 1,2,4-Triazole Nucleosides.
Certain derivatives of this latter compound have also been found to have significant activity against these viruses, and it has also been discovered that the triazole bases of certain of such compounds, 1,2,4 -triazole-3-carboxamide and 1,2,4-triazole-3-thiocarboxamide, likewise have significant antiviral activity against these respiratory viruses. The chemical structure and synthesis of each compound has been previously reported (Latvijas PSR Zinatnu Akad. Vestis, Kim. Ser., 1965, (2) 204-208 See Chem. Abst. 63, 13243 (1965).
It has also now been discovered that 1,2,4-triazole-3-carboxamide may be caused to undergo enzymatic conversion to 1-.beta.-D-ribofuranosyl- 1,2,4-triazole-3-carboxamide, the aforenoted nucleoside which is a significantly effective antiviral compound. As will be shown hereinafter, the triazole base may be reacted with the enzyme Nucleoside Phosphorylase to effect the indicated conversion.